Electrocatalytic reduction of chromium by poly(aniline-co-o-aminophenol): An efficient and recyclable way to remove Cr(VI) in wastewater

Poly(aniline-co-o-aminophenol) (PANOA)-modified glassy carbon electrode (GCE) was first used to investigate the electrocatalytic reduction of dichromate in a NaCl solution of pH 5.0. The results of cyclic voltammograms and UV–vis spectra demonstrated that the reduction of Cr(VI) occurred at PANOA-modified GCE. The FT-IR, ESR and XPS results showed that the Cr(VI) can be doped in the PANOA films and can convert to less-toxic Cr(III). The doping level Cr/N was 78.2% and trace amount of Cl (0.42%) was detected in the doped PANOA, which indicated that the doping process is effective and PANOA had rather good ion selectivity in the 0.10 M NaCl supporting electrolyte. The factors influenced the reduction were also considered. Various initial concentrations of Cr(VI) had different removal rates. The maximum removal rate of Cr(VI) at 20 mg L⁻¹ (32.3%) was better than that of at 5 mg L⁻¹ (22.9%). The solution pH had little effect on Cr(VI) reduction and doping process of the PANOA because PANOA had good electrochemical activity and stability in a wide range of pHs (from pH 4 to pH 8).